Computer disk drives store information on magnetic disks. Typically, the information is stored on each disk in concentric tracks that are divided into sectors. Information is written to and read from a disk by a transducer that is mounted on an actuator arm capable of moving the transducer radially over the disk. Accordingly, the movement of the actuator arm allows the transducer to access different tracks. The disk is rotated by a spindle motor at high speed which allows the transducer to access different sectors on the disk.
A conventional disk drive, generally designated 10, is illustrated in FIG. 1. The disk drive comprises a disk 12 that is rotated by a spin motor 14. The spin motor 14 is mounted to a base plate 16. An actuator arm assembly 18 is also mounted to the base plate 16.
The actuator arm assembly 18 includes a transducer 20 mounted to a flexure arm 22 which is attached to an actuator arm 24 that can rotate about a bearing assembly 26. The actuator arm assembly 18 also contains a voice coil motor 28 which moves the transducer 20 relative to the disk 12. The spin motor 14, voice coil motor 28 and transducer 20 are coupled to a number of electronic circuits 30 mounted to a printed circuit board 32. The electronic circuits 30 typically include a read channel chip, a microprocessor-based controller and a random access memory (RAM) device.
The disk drive 10 typically includes a plurality of disks 12 and, therefore, a plurality of corresponding actuator arm assemblies 18. However, it is also possible for the disk drive 10 to include a single disk 12 as shown in FIG. 1.
FIG. 2 is a functional block diagram which illustrates a conventional disk drive 10 that is coupled to a host computer 33 via an input/output port 34. The disk drive 10 is used by the host computer 33 as a data storage device. The host 33 delivers data access requests to the disk drive 10 via port 34. In addition, port 34 is used to transfer customer data between the disk drive 10 and the host 33 during read and write operations.
In addition to the components of the disk drive 10 shown and labeled in FIG. 1, FIG. 2 illustrates (in block diagram form) the disk drive's controller 36, read/write channel 38 and interface 40. Conventionally, data is stored on the disk 12 in substantially concentric data storage tracks on its surface. In a magnetic disk drive 10, for example, data is stored in the form of magnetic polarity transitions within each track. Data is “read” from the disk 12 by positioning the transducer 20 above a desired track of the disk 12 and sensing the magnetic polarity transitions stored within the track, as the track moves below the transducer 20. Similarly, data is “written” to the disk 12 by positioning the transducer 20 above a desired track and delivering a write current representative of the desired data to the transducer 20 at an appropriate time.
The actuator arm assembly 18 is a semi-rigid member that acts as a support structure for the transducer 20, holding it above the surface of the disk 12. The actuator arm assembly 18 is coupled at one end to the transducer 20 and at another end to the VCM 28. The VCM 28 is operative for imparting controlled motion to the actuator arm 18 to appropriately position the transducer 20 with respect to the disk 12. The VCM 28 operates in response to a control signal icontrol generated by the controller 36. The controller 36 generates the control signal icontrol, for example, in response to an access command received from the host computer 33 via the interface 40 or in response to servo information read from the disk surface 12.
The read/write channel 38 is operative for appropriately processing the data being read from/written to the disk 12. For example, during a read operation, the read/write channel 38 converts an analog read signal generated by the transducer 20 into a digital data signal that can be recognized by the controller 36. The channel 38 is also generally capable of recovering timing information from the analog read signal. During a write operation, the read/write channel 38 converts customer data received from the host 33 into a write current signal that is delivered to the transducer 20 to “write” the customer data to an appropriate portion of the disk 12. As will be discussed in greater detail, the read/write channel 38 is also operative for continually processing data read from servo information stored on the disk 12 and delivering the processed data to the controller 36 for use in, for example, transducer positioning.
FIG. 3 is a top view of a magnetic storage disk 12 illustrating a typical organization of data on the surface of the disk 12. As shown, the disk 12 includes a plurality of concentric data storage tracks 42, which are used for storing data on the disk 12. The data storage tracks 42 are illustrated as center lines on the surface of the disk 12; however, it should be understood that the actual tracks will each occupy a finite width about a corresponding centerline. The data storage disk 12 also includes servo information in the form of a plurality of radially-aligned servo spokes 44 (or wedges) that each cross the tracks 42 on the disk 12. The servo information in the servo spokes 44 is read by the transducer 20 during disk drive operation for use in positioning the transducer 20 above a desired track 42 of the disk 12. Among other things, the servo information includes a plurality of servo bursts (e.g., A, B, C and D bursts or the like) that are used to generate a Position Error Signal (PES) to position the write head relative to a track's centerline during a track following operation. The portions of the track between servo spokes 44 are used to store customer data received from, for example, the host computer 33 and are referred to as customer data regions 46.
It should be understood that, for ease of illustration, only a small number of tracks 42 and servo spokes 44 have been shown on the surface of the disk 12 of FIG. 3. That is, conventional disk drives include one or more disk surfaces having a considerably larger number of tracks and servo spokes.
During the disk drive manufacturing process, a special piece of equipment known as a servo track writer (STW) is used to write the radially-aligned servo information which forms servo spokes 44. A STW is a very precise piece of equipment that is capable of positioning the disk drive's write head at radial positions over the disk surface, so that servo information is written on the disk surface using the disk drive's write head with a high degree of positional accuracy.
In general, a STW is a very expensive piece of capital equipment. Thus, it is desirable that a STW be used as efficiently as possible during manufacturing operations. Even a small reduction in the amount of data needed to be written by the STW per disk surface can result in a significant cost and time savings.
A STW is used to write servo information, by controlling the position of the disk drive's write head, on a disk surface in a circumferential fashion at each radius at which the disk drive's write head is positioned. During drive operation, the servo information is used to position the transducer of the disk drive over the appropriate data track and data sector of the disk. Accordingly, as the number of tracks per inch (TPI) increases, the amount of time necessary to write servo information increases. That is, the number of circumferential passes that a STW must make over a disk surface increases as TPI increases. Thus, unless more STWs are supplied, manufacturing times will continually increase as the TPI increases.
Instead of using a STW to write servo information in a circumferential fashion at each radius, the assignee of the present embodiments presently uses a STW to write servo information in a spiral fashion (in at least some if its disk drives). Specifically, the STW moves the write head in a controlled manner (e.g., at a constant velocity or along a velocity profile) from the outer diameter of the disk to the inner diameter of the disk (or visa-versa) as the disk spins.
FIG. 4 is a diagrammatic representation of a disk surface 210 having a first spiral of servo information 215 written thereon. The dashed line, identified by reference numeral 220, represents a track. The first spiral of servo information 215 may make multiple revolutions around the disk surface 210 (roughly two revolutions as shown in FIG. 4), but only crosses track 220 once.
FIG. 5 is a diagrammatic representation of a disk surface 210 having a first spiral of servo information 215 and a second spiral of servo information 225 written thereon. As shown in FIG. 5, the first and second spirals 215, 225 are interlaced with one another and are written approximately 180 degrees apart. Again, each spiral crosses track 220 only once.
Additional spirals of servo information may be written on the disk surface 210 depending upon the servo sample rate (that is, the number of servo samples required for each track 220 to keep the disk drive's transducer sufficiently on-track). For example, if a servo sample rate of 120 equally-spaced servo sectors per track was required, 120 equally-spaced spirals may be written on the disk surface 110. Accordingly, by writing servo information in a spiral fashion, the time necessary to write servo information on disk surface 110 using the STW is a function of the number of spirals of servo information to be written, rather than the number of tracks.
Referring again to FIGS. 4 and 5, the spirals of servo information are written by moving the disk drive's write head using the STW in a generally radial direction (more accurately, in a radial direction along an arc due to the position of the bearing assembly), while both the disk is spinning and the write head is enabled. The direction of disk rotation is indicated by an arrow as shown in each of FIGS. 4 and 5.
The disk drive's write head is enabled for its entire stroke (i.e., from OD to ID or visa-versa) while under the control of the STW. As a result, a continuous spiral of servo information is written.
Each of the spirals of servo information includes sync marks written at fixed time intervals by the disk drive's write head. As mentioned above, the STW is used to move the disk drive's write head at some fixed velocity (or velocity profile) in a generally radial direction across the disk surface. If the time interval between sync marks is known and the velocity of the disk drive's write head is known, the distance between sync marks along a spiral can be determined. Specifically, the following formula may be applied: Distance=(STW Velocity)(Time), where Distance represents the radial distance between sync marks, Velocity represents the radial velocity of the disk drive's write head (under control of the STW) and Time represents the interval between sync marks.
For example, the interval between sync marks may be set at 1 microsecond, while the write head may be controlled to move at a radial velocity of 1 inch per second along its stroke. Thus, the radial distance between sync marks can be calculated to be 1 microinch along each spiral.
Each sync mark along a given spiral corresponds to a unique radius. Accordingly, the sync marks may be used to accurately position a transducer of a disk drive over the disk surface.
U.S. patent application Ser. No. 10/859,062 filed Jun. 2, 2004 (incorporated herein by reference) describes a method and apparatus for performing a self-servo write operation in a disk drive. Reference is now made to FIG. 6, which describes a self-servo write operation that is disclosed in the aforementioned patent application.
At a first station (e.g., a STW station), a STW is used to write spirals of servo information onto the disk surface by moving a write head in a controlled (closed-loop) manner (e.g., at a constant velocity or along a velocity profile) across the disk surface while the disk is spinning (step 610).
After all of the spirals have been written, a small band of conventional servo information (e.g., embedded servo information) is written onto the disk surface (e.g., near its inner diameter or the outer diameter) using the STW (step 620). In one case, a portion of the small band of conventional servo information is written at a radial location that overlaps with a radial location where spiral servo information has been written.
The small band of conventional servo information provides an absolute reference point (in both the radial and circumferential sense) on the disk surface. More specifically, conventional servo sectors in the small band of conventional servo information include both a track number (to provide a radial reference point) and a sector number (to provide a circumferential reference point). Final servo patterns may be written relative to this absolute reference point.
It should be understood that there are other techniques for providing an absolute reference point on the disk surface. One such technique is described in U.S. patent application Ser. No. 10/859,061 filed Jun. 2, 2004, which is incorporated herein by reference. U.S. Provisional Patent Application Ser. No. 60/475,126 filed Jun. 2, 2003 (from which the above-identified patent application claims priority) is also incorporated by reference.
Next, the disk drive is moved out of the first station and into another station, so as to free-up the STW for other disk drives. At the second station (e.g., a script write station), which includes a host connection, self-servo writing instructions and other information (e.g., drive firmware, self-test script, read channel parameter tables and defect management lists) are written into a utility zone, which is comprised of a portion (e.g., a few tracks) of the small band of conventional servo information (step 630).
In one case, the self-servo writing instructions and other information may be written to a temporary utility zone and then moved to a final (or permanent) utility zone as discussed in U.S. patent application Ser. No. 10/859,058 filed on Jun. 2, 2004, which is incorporated herein by reference. U.S. Provisional Patent Application Ser. No. 60/475,097 filed Jun. 2, 2003 (from which the above-identified patent application claims priority) is also incorporated by reference. The temporary utility zone (or temporary utility area) and the permanent utility zone (or permanent utility area) are shown in FIG. 6A, which is described below.
It should be noted that, prior to writing any information into the utility zone, the read head becomes ready on the small band of conventional servo information and the small band of conventional servo information (including the utility zone) is scanned for defects. Areas containing flaws are mapped out, so that they will not be used.
There are several techniques for bringing the read head to a ready position on the small band of servo information. One technique is described in U.S. Provisional Patent Application Ser. No. 60/475,039 entitled “BEMF Controlled Push Off/Acquire” filed Jun. 2, 2003, which is incorporated herein by reference.
Next, the disk drive is moved to a third station (e.g., a self-test station), where no host connection or other mechanical components need to access the drive. The disk drive is powered-on (e.g., with its normal supplies of +12V and +5V) and reads the self-servo writing information included in the utility zone, so as to undergo a self-servo write process using the spirals of servo information (step 640). In one embodiment, the final servo pattern looks like the conventional servo pattern of FIG. 3.
It should be noted that, prior to reading the self-servo writing information, the read head becomes ready (as in station 2) on the small band of servo information and locks to the absolute reference point (i.e., in time and position). Then, the drive code, manufacturing diagnostic code and self-test script (among which the self-servo writing information is included) are read.
Although three different stations were described, it should be understood that other configurations are possible. That is, more or less stations may be provided and certain operations may be combined or divided between stations.
It should also be understood that features described herein may be used in the absence of writing a small band of conventional servo information onto the disk surface.
FIG. 6A is a simplified diagrammatic representation of a portion of a disk surface 210, wherein the disk surface 210 is shown in linear, instead of arcuate, fashion for ease of depiction. The disk surface 210 has an inner diameter (ID), an outer diameter (OD), an area of STW-written servo information 660, an area of self-servo written servo information 670, a temporary utility zone 680 and a permanent utility zone 690.
The area of STW-written servo information 660 is the small band of conventional servo information, discussed above. The temporary utility zone 680 is located within the area of STW-written servo information 660.
The area of self-servo written information 670 formerly included spirals of servo information, discussed above. The permanent utility zone 690 is located within the area of self-servo written servo information 670. It should be noted that, for clarity, FIG. 6A is not drawn to scale.
At least one prior technique requires drives to be identified before the script write process. Such technique also requires the drives to be routed to use different sets of scripts, codes or even different production lines. One prior process flow is shown in FIG. 7.
Disk drives (both newly built and reprocessed drives) are delivered to the script write station (step 705). Each disk drive includes a serial number capable of being read by a bar code scanner (or similar device). At the script writer, each disk drive (regardless of whether it is a new built drive or reprocessed drive) is scanned by an operator using a barcode scanner (step 710). The serial number of the drive is cross-referenced with a FIS (factory information system) database. A determination is made, based upon the information in the FIS database, as to whether the drive is a newly built drive or not (step 715).
If the drive is a newly built drive, then the operator routes the drive to a new build line and the drive is processed with script B (step 720). More specifically, script B includes the information necessary for the drive to perform a self-servo write operation, which is written into the temporary utility area. The drive then undergoes self-test procedures and a determination is made as to whether the drive failed or passed such self-test procedures (step 725).
If the drive passes the self-test procedures, then the drive is considered to be a finished good (step 790). If the drive fails the self-test procedures, a disposition action is carried out based upon the reason for the failure (e.g., if the drive failed due to a bad head, then the head may be changed). Then, the drive is again delivered to the script write station (step 705).
After the drive's serial number is cross-referenced with the FIS database (step 710), a determination is made as to whether the drive is a newly built drive (step 715). In this case, since the drive is not a newly built drive, the operator routes the drive to a reprocess line, which is a different line in production.
A determination is then made as to whether the drive failed during the self-propagation (or fill) process (step 730). This information is provided from the FIS database. If the drive failed during fill process, the disk drive is processed with script A (step 735), which is different from script B. Script A includes the information necessary to perform a self-servo write operation.
The drive then undergoes self-test procedures and a determination is made as to whether the drive failed or passed such self-test procedures (step 740). If the drive passes the self-test procedures, then the drive is considered to be a finished good. If the drive fails the self-test procedures, a disposition action is carried out based upon the reason for the failure (e.g., if the drive failed due to a media problem, then the media may be changed and the media may be required to be sent back to the STW to have servo information placed on it). Next, the drive is again delivered to the script write station (step 705).
If the drive did not fail during the fill process of step 730, then the drive is processed with script C (step 745), which is different from script B and script A. Specifically, script C does not include information necessary to perform a self-servo write operation, since it is likely that the fill has already been performed.
The drive then undergoes self-test procedures and a determination is made as to whether the drive failed or passed such self-test procedures (step 750). If the drive passes the self-test procedures, then the drive is considered to be a finished good. If the drive fails the self-test procedures, a disposition action is carried out based upon the reason for the failure. Next, the drive is again delivered to the script write station (step 705).
The process described in connection with FIG. 7 has several disadvantages. First, two different manufacturing lines are required, namely, a new build line and a reprocess line. In one case, there may be seven new build lines and one reprocess line.
Second, three sets of scripts are required to be maintained (e.g., scripts A, B, and C). Accordingly, whenever a change is made to one of the scripts, corresponding changes must be made to the other scripts.
Third, operator intervention is required to determine whether the drive is a newly built drive or a reprocessed drive. Accordingly, valuable manpower is being wasted, as compared to using an automated system, and the process is subject to human error.
In view of the above, factory productivity may be reduced, resource costs may be increased, and the complexity of the process may be increased.
Accordingly, it would be useful to provide a method and apparatus for performing a spiral self-servo write operation in a disk drive using an auto detection scheme.